feat: add MPTCP support

[AkinoKaede]

Background

Multipath TCP or MPTCP is an extension to the standard TCP and is described in RFC 8684. It allows a device to make use of multiple interfaces at once to send and receive TCP packets over a single MPTCP connection. MPTCP can aggregate the bandwidth of multiple interfaces or prefer the one with the lowest latency.

MPTCP is support in Go 1.21

Checklist

• [x] The Pull Request has been fully tested
• [ ] There's an entry in the CHANGELOGS
• [ ] There is a user-facing docs PR against https://github.com/daeuniverse/dae

Full Changelogs

• Add MPTCP support for nodes and subscription requests
• Update config description
• Update daeuniverse/outbound to latest

Issue Reference

Closes #595

Test Result

sudo ip mptcp monitor